Strain symmetrization effects in pseudomorphic Si_1-yC _y/Si_1-xGe_x superlattices

We report on strain and stability measurements on pseudomorphic Si 1-yCy/Si1-xGex superlattices which are synthesized by solid source molecular beam epitaxy on silicon (100) substrate. The strain in the superlattices alternates between tensile and compressive in the individual Si1-yCy and Si 1-xGex alloy layers, respectively. A symmetrical strain distribution can be achieved directly on silicon by adjusting the carbon and the germanium content and/or the thickness of the individual layers. X-ray diffraction and transmission electron microscopy are applied to investigate the structural properties and the thermal stability.